High temperature alloys



United States Patent This is a continuation-in-part of application Serial No. 119,902, filed June 27, 1961, now Patent No. 3,165,400.

This invention relates to austenitic alloys for high temperature applications of the general character disclosed and claimed in the copending application of Amedee Roy,

one of the present applicants, and Walter E. Jominy, Serial No. 119,902, filed June 27, 1961, which by this cross reference is made a part hereof, and especially to such composition made to include or exclude trace amounts of certain elements in order to improve the elevated tempera ture properties of the compositions and/ or minimize variations in the properties between heats of apparently the same composition.

Early work with alloys of the above type had often shown a wide range in properties between heats of apparently the same composition (insofar as the elements thereof could be readily analyzed by conventional techniques). It was theorized that trace elements picked up either from the raw materials or the melting crucible were strongly influencing elevated temperature properties and preventing consistent properties from being attained. Their effect often was to lower the property values expected of the alloy in the absence of these effects.

Extensive investigations were conducted to investigate the effects of various beneficial or detrimental trace elements that could possibly be present in the alloy. To this end small melts (approximately 3600 gms.) were prepared of the purest raw materials (commercial grades) available plus small additions of one of the following elements: B, Zr, Ti, Ta, P, S, and Al. For example, six heats of pure materials were prepared with Zr additions ranging from 0.005 to 1% by weight and similar heats were prepared with the others. In some cases two of the trace elements, for instance Zr and B were added together to determine if their effects were complimentary or additive. Moreover similar melts were prepared in four different types of melting crucibles: A1 0 MgO, Zircon (Zr O -SIO and graphite. The small heats were cast into investment molds (both solid and shell type) containing approximately ten test bar cavities GA" .dia. gage section). These cast to size test bars were utilized to determine the elevated temperature properties of the heats.

Table I shows the composition of the alloys tested and the amounts of trace elements included. The amount of iron (Fe) is not shown, it constituting essentially the remainder thereof.

Table H shows the stress rupture life under various loads and the stress for a rupture life of 100 hours, at

the indicated temperature to provide a convenient basis for comparison.

The composition of a typical heat before adding any of the trace elements may be seen from heat No. 267D.

With respect to zirconium (Zr) it will be noted from heats 293D, 272D, 273D, 277D, 320D, and 321D in Tables I and II for example, representing compositions containing respectively 0.005, 0.01, 0.1, 0.25, 0.5 and 1.0 weight percent zirconium added to the base composition 267D that best results were obtained with heat 273D containing 0.1 zirconium. It was noted too that single additions of zirconium up to 1.0% did not substantially adversely affect the basic composition property. In Table II the letter A appearing after the heat number means that the as-cast alloy was solution heat treated at 2250" F. for /2 hour and aged at 1400 F. for 20 hours after air cooling.

With respect to boron (B), it will be noted from heats,

292D, 285D, 268D, 286D and 269D in Tables I and II, for example, representing compositions containing respectively 0.002, 0.005, 0.01, 0.025 and 0.05 weight percent boron added to the 'base composition 267D that the optimum properties in the A (solution treated and aged) condition as shown in Table II was obtained with heat 285D containing 0.005 boron. The proper-ties of heats 286D and 269D containing 0.025 and 0.05 boron were adversely affected by these amounts of boron. It would appear that up to about 0.025% boron may be safely used in the base composition 267D preferably up to about 0.01%. For the same heats in as cast condition those containing 0.025% and above were inferior to those containing less than this amount of boron. The use of boron is especially desirable because it appears to promote an optimum distribution of the precipitates and an optimum structure With respect to a combination of boron and zirconium heats 274D, 275D, 278D and 279D it appeared that the combination in the optimum amount used separately did not produce any improved properties in the base alloy containing single additions of these elements.

With respect to trace elements phosphorous, sulfur, titanium, tantalum and aluminum as reported by heats 290D, 291D, 322D, 323D, 299D, 301D, 295D, 296D, 297D and 324D, 388D, 389D and 391D, it appears that trace amounts of these elements are not detrimental. However, 2% or more titanium is detrimental and phosphorous additions at 0.5% and above produced alloys which did not respond to heat treatment.

With respect to the crucibles used for melting the heats it was found that part of all of the trace elements given above may be picked up therefrom. Heats 243D, 246D, 247D and 248D were, for example, prepared using respectively graphite, alumina, zircon, and zircon crucibles and picked up at least some of the trace elements therefrom. Most of the other heats were prepared in magnesia crucibles which are less likely to impart the trace elements to the heats.

Table I.Chemical compositions of heat (nominal weight percent) Alloy C Cr Si W Mo Cb Ni Mn N B Others 243D Q- 1. 0 18. 0 0. 5 2. 0 2. 0 2. 0 5. 0 5. 0 0.3 Graphite crucible.

246D 1. O 18. 0 0. 5 2. O 2. 0 2. 0 5. 0 5. 0 0.3 Alumina.

crucible.

247D 1. 0 18. 0 0. 5 v2. 0 2. 0 2. 0 5. 0 5. 0 0.3 Zirconia crucible.

263D- 1. 0 18.0 0. 5 2. 0 2. 0 2. 0 5. 0 5. 0 0.3 0.1 Ti.

265D 1.0 18.0 0.5 2.0 2.0 2.0 5.0 5.0 0.3 0.5 Ti.

267D 1.0 18.0 0.5 1.0 1.0 1.0 5.0 5.0 MgO crucible.

Stress-rupture data at 1,500 F.

Stress 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 m 5 5 5 5 m 0 0 0 w 5 5 0 5 0 8 5 1 y 1 y 1 1 2 0 1 7 1 0 9 0 9 0 0 0 9 4 9 5 9 L 3 2 3 2 3 2 2 2 2 2 3 2 2 2 2 2 2 h 0 0 1 03342 093432 9 32 0 0 3 46 332 m r. 1 ED 60810 406782 031252 437159 77349 6843 LumooJml 09035 32 8 39m 3* om 7 42 0 4 om7 5oo e 5999 18366 518%43 81 .5%1 9 075 0383 m 1 2 1 11 3 1 l 2 4 1 2 2 T 00000 000000 000000 000000 00000 0000 00000 000000 0000 00 0 0 00000 0000 00000 000000 wm0000 00m0m0 00 00 0000 5 5 2 0 0 0 5 7 5 2 0 7 0 5 2 7 5 7 0 5 0 7 5 7 2 0 7 5 7 0 7 23333 322333 232%32 223232 22232 2232 Alloy 1. An iron base casting type alloy for producing products of complex shape and having substantial oxidation resistance and high strength at elevated temperature and characterized by a structure having a network outlining an austenitic phase embedding fine dot-like precipitates, 5 said alloy consisting essentially of by weight percent, about 0.6 to 1.6% carbon; about 12 to 35% chromium; between 0 to 2.5% silicon; between 0.2 to 12% of a plurality of carbide forming elements from the group consisting of tungsten in the range 0.1 to 10%, molybdenum in'the range 0.1 to 9%, columbium and tantalum,

said columbium and tantalum combined being in the range 0.1 to 5%, up to 15% of metal from the group consisting of, nickel in the range 0 to 15%, manganese in .the range 0 to 15%, cobalt in the range 0 to 8% 27,000 0 to 0.6% nitrogen; a small but eifective amount of boron not exceeding 0.025% to promote distribution of the precipitates; the balance essentially iron, said iron content being at least 40%, said nickel being at least about 2% when said manganese is less than about 1%, 500 said manganese being at least between 2 to 10% when the nickel is less than 2% and nitrogen is present, at least between about 5 to 10% when substantially no nitrogen present and the nickel is less than about 2%, and at least about 10% when the nickel is zero.

Stress-rupture data at1,500 F.

Table Il-Continued a 1 C n e h m m n D" w w 5 6 m 0 S 2 9 W a 3 w 3 1 O 5 0 Ku 0 PO 0 5 1 1 3 3 4 4 5 7 0 0 0 0 0 0 0 0 0 0 0 0 0 0 P 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 E m w m m 0 w m m 5 5 0 5 0 m 5 5 0 5 5 5 1 1 a y 1 1 co y y I 0 5 0 5 8 oo 7 4 4 4 0 J 2" H m m m m M 3 2 3 2 2 2 2 2 2 2 2 r. 2 h 0 0 1 5 5 5 y 1757 9522774 055200 018111 awm 47112 U%..m1257 M %B% 533 211 33 1111 1 1 11 nm r. 1 ED. 71029 2055395 038374 7081622 288143 476618 6248725 6653 5 5 052991 3 7 5 0 9 43 92232 9 omn rhlomnmd 5 9m7 &0 flm OWHQA ZLRW 0 793597 103 44 7 12 99 1 3132 3 493 8 258 17 m 54 13 0 u 7m1577 6m17 3626M 11 4 2 2 T 00000 000000 000000 0000000 000000 000000 0000000 000000 000000 00 00 000000 000000 0000000 000000 000000 00 wmmmm mmmwmm mwmmmm WWWWOOW 000000 000000 0000000 000000 000000 00 S v I 1 y 7 y i 1 1 i y 1 i 1 1 y y y y 1 7 i 1 1 y i y y 1 i 1 1 y y y y i D 1 1 y 1 i r y y i 520 0 55200 075520 075520 0755520 075077 075075 07 m W%333 o n 23333 322333 322333 3222333 322322 322322 32 t s n u u u u n n u u n u n a u 0 n u n u u n n u n u n n V. o m m n n u u n I n A D D D WD MMMD D D D D D D D D D DD w 1111111 2 3 5 6 9 1 0 2 3 4 55 9999999 9 9 9 9 0 2 2 2 2 22 2222222 2 2 WW 2 2 3 3 3 3 3 33 2. An iron base alloy as claimed in claim 1 wherein ,a test bar thereof A in diameter exposed to 1500 F.

carbide forming elements from the group consisting of tungsten in the range 0.1 to 10%, molybdenum in the range 0.1 to 9%, columbium and tantalum, said columbium and tantalum combined being in the range 0.1 to 5 up to 15% of metal from the group consisting of, nickel in the range to 15 manganese in the range 0 to 15%, cobalt in the range 0 to 8%; 0 to 0.6% nitrogen; 21 small but efiective amount of zirconium not exceeding 1.0% to promote the 100 hour stress rupture strength at 1500" F. of the alloy when heat treated; the balance essentially iron, said iron content being at least 40%, said nickel being at least about 2% when said manganese is less than about 1%, said manganese being at least between 2 to 10% when the nickel is less than 2% and nitrogen is present, at least between about 5 to when substantially no nitrogen is present and the nickel is less than about 2%, and at least about 10% when the nickel is zero.

4. An iron base casting type alloy for producing prod ucts of complex shape and having substantial oxidation resistance and high strength at elevated temperature, said alloy consisting essentially of, by weight percent, about 0.6 to 1.6% carbon; about 12 to 35% chromium; between 0 to 2.5% silicon; between 0.2 to 12% of a plurality of carbide forming elements from the group consisting of tungsten in the range 0.1 to 10%, molybdenum in the range 0.1 to 9%, columbium and tantalum, said columbium and tantalum combined being in the range 0.1 to 5%, up to 15 of metal from the group consisting of, nickel in the range 0 to 15%, manganese in the range 0 to 15%, cobalt in the range 0to 8%; 0 to 0.6% nitrogen; about 0.001 to 0.025% boron; about 0.005 to 0.1% zirconium; the balance essentially iron, said iron content being at least 40%, said nickel being at least about 2% when said manganese is less than about 1%, said manganese being at least between 2 to 10% when the nickel is less than 2% and nitrogen is present, at least between about 5 to 10% when substantially no nitrogen is present and the nickel is less than about 2%, and at least about 10% when the nickel is zero.

, 5. An iron base casting type alloy for producing products of complex shape and having substantial oxidation resistance and high strength at elevated temperature, said alloy consisting essentially of,'byweight percent, about 0.6 to 1.6% carbon; about 12 to 35% chromium; between 0 to 2.5% silicon; between 0.2 to 12% of a plurality of carbide forming elements from the group consisting of tungsten in the range 0.1 to 10%, molybdenum in the range 0.1 to 9%, colurnbium and tantalum, said oolumbium and tantalum combined being in the range 0.1 to 5%, up to 15% of metal from the group consisting of, nickel in the range 0 to 15 manganese in the range 0 to 15%, cobalt in the range 0 to 8%; 0 to 0.6% nitrogen; about 0.001 to 0.025% boron; up to 2% titanium; up to 0.5 phosphorous; the balance essentially iron, said iron content being at least 40%, said nickel being at least about 2% when said manganese is less than about 1%, said manganese being at least between 2 to 10% when the nickel is less than 2% and nitrogen is' present, at least between about 5 to 10% when substantially no nitrogen is present and the nickel is less than about 2%, and at least about 10% when'the nickel is zero.

6. An iron base alloy as claimed in' claim 3 wherein a test bar thereof /4" in diameter exposed to 1500 F. for 100 hours is generally characterized by a structure having an interdendritic network of substantially lederburite phases outlining an austenitic phase embedding relatively fine dot-like precipitates randomly distributed therein.

7. An iron base casting type alloy for producing prod ucts of complex shape and having substantial oxidation resistance and high strength at elevated temperature, said alloy consisting essentially of, by weight percent, about 0.6 to 1.6% carbon; about 12 to 35% chromium, be tween 0 to 2.5 silicon; between 0.2 to 12% of a plurality of carbide forming elements from the group consisting of tungsten in the range 0.1 to 10%, molybdenum in the range 0.1 to 9%, columbium and tantalum, said columbium and tantalum combined being in the-range 0.1 to 5%, up to 15 of metal from the group consisting of, nickel in the range 0 to 15 manganese in the range 0 to 15%, cobalt in the range 0 to 8%, 0 to 0.6% nitrogen; about 0.001 to 0.01% boron; the balance essentially iron, said iron content being at least 40%, said nickel being at least about 2% when said manganese is less than about 1%, said manganese being at least between 2 to 10% when the nickel is less than 2% and nitrogen is present, at least between about 5 to 10% when substantially no nitrogen is present and the nickel is less than about 2%, and at least about 10% when the nickel is zero.

References Cited by the Examiner UNITED STATES PATENTS 3,165,400 [/1965 Roy et al. 126

DAVID L. RECK, Primary Examiner. 

1. AN IRON BASE CASTING TYPE ALLOY FOR PRODUCING PRODUCTS OF COMPLEX SHAPE AND HAVING SUBSTANTIAL OXIDATION RESISTANCE AND HIGH STRENGTH AT ELEVATED TEMPERATURE AND CHARACTIERIZED BY A STRUCTURE HAVING ANETWORK OUTLINING AN AUSTENITIC PHASE EMBEDDING FINE DOT-LIKE PRECIPITATES, SAID ALLOY CONSISTING ESSENTIALLY OF BY WEIGHT PERCENT, ABOUT 0.6 TO 1.6% CARBON; ABOUT 12 TO 35% CHROMIUM; BETWEEN 0 TO 2.5% SILICON; BETWEEN 0.2 TO 12% OF A PLURALITY OF CARBIDE FORMING ELEMENTS FROM THE GROUP CONSISTING OF TUNGSTEN IN THE RANGE 0.1 TO 10%, MOLYBDENUM IN THE RANGE 0.1 TO 9%, COLUBIUM AND TANTALUM, SAID COLUMBIUM AND TANTALUM COMBINED BEING IN THE RANGE 0.1 TO 5%, UP TO 15% OF METAL FROM THE GROUP CONSISTING OF, NICKEL IN THE RANGE 0 TO 15%, MANGANESE IN THE RANGE 0 TO 15%, COBALT IN THE RANGE O TO 8%; 0 TO 0.6% NITROGEN; A SMALL BUT EFFECTIVE AMOUNT OF BORON NOT EXCEEDING 0.025% TO PROMOTE DISTRIBUTION OF THE PRECIPITATES; THE BALANCE ESSENTIALLY IRON, SAID IRON CONTENT BEING AT LEAST 40%, SAID NICKEL BEING AT LEAST ABOUT 2% WHEN SAID MANGANESE IS LESSTHAN ABOUT 1%, SAID MANGANESE BEING AT LEAST BETWEEN 2 TO 10% WHEN THE NICKEL IS LESSS THAN 2% AND NITROGEN IS PRESENT, AT LEAST BETWEEN ABOUT 5 TO 10% WHEN SUBSTANTIALLY NO NITROGEN IS PRESENT AND THE NICKEL IS LESS THAN ABOUT 2%, AND AT LEAST ABOUT 10% WHEN THE NICKEL IS ZERO. 